It has been previously proposed to use steps in hulls to reduce the area of engagement between the hull of a boat and the water, thereby increasing the speed of the boat. Such hulls have been used on racing boats, on plane floats, and on amphibious plane hulls. However, these steps are not directly exposed to the atmosphere, and require a certain minimum speed, a very powerful engine and expenditure of substantial amounts of energy to get the hull up "on the step" sufficiently high to allow air under the hull to break the vacuum, or water-to-hull contact in the area immediately behind the vertical portion of the step. This phenomenon is apparent from the observed fact that it takes a float plane a much greater distance to take off from the water when the water is calm than when it is choppy. If the water is choppy, the step is exposed to the atmosphere in the valley between the waves, thus breaking the vacuum or the contact between the float and the water much sooner, thereby increasing the speed as the wetted area of the float decreases, and enabling a much shorter takeoff distance. The friction of a hull in water is a function of the wetted area of the hull, and the function of the step is to reduce the wetted area. Unfortunately, in most of the hull designs which have been proposed up to the present time, the boat hull is not easily brought up onto the step and this limits the usefulness of the stepped hull concept.
Prior stepped hull configurations of one type or another are disclosed in U.S. Pat. Nos. 1,050,517; 1,296,155; and 3,874,315.